A sealing material has been conventionally blended with a stabilizer in order that weather resistance may be imparted to the material. However, irrespective of the above fact, such whitening problems as described below occur, and have been serious problems to be solved in the field of sealing material construction. One of the whitening problems is as described below. When a masking tape is stuck on a portion apart from a joint of an adherend due to an error in construction at the time of the placement of the sealing material, thin layer parts are formed after spatulation for flattening the surface of the sealing material at a joint portion, and the thin layer parts each deteriorate to whiten more quickly than the sealing material at the joint portion, with the result that the appearance of a structure becomes poor, and the design of the structure becomes extremely bad.
At present, there is no technology for solving the whitening phenomenon of those thin layer parts (hereinafter collectively referred to as “thin layer portion”). Details about the foregoing are as described below. Conventionally known examples of a stabilizer having good weather resistance to be blended into the sealing material include a combination of a benzotriazole based ultraviolet ray absorbing agent and a hindered phenol based antioxidant as described in Patent Document 1, a combination of a benzotriazole based ultraviolet ray absorbing agent and a specific hindered amine based light stabilizer as described in Patent Document 2, and a combination of a benzotriazole based ultraviolet ray absorbing agent and a hindered amine based light stabilizer containing a specific triazine skeleton as described in Patent Document 3. Those stabilizers are effective for, for example, sealing materials at thick (for example, 5 mm or more in thickness) joint portions (hereinafter collectively referred to as “thick layer portion”), but none of those stabilizers is effective for the thin layer portion, and no stabilizer formulation capable of improving the weather resistance of the thin layer portion and that of the thick layer portion simultaneously is known.
In view of the foregoing, in the field of sealing materials, there is a demand for a sealing material designed so that a thin layer portion is prevented from deteriorating to whiten more quickly than a thick layer portion, and, at the same time, the thick layer portion exerts excellent weather resistance. Patent Document 4 describes that a combination of a benzotriazole based ultraviolet ray absorbing agent, a hindered amine based compound having a molecular weight of 200 to 1,000 and free of a triazine skeleton in any one of its molecules, and a hindered amine compound having a triazine skeleton in any one of its molecules as light stabilizers is a stabilizer formulation having good weather resistance in each of a thin layer portion, and a thick layer portion. However, it cannot yet be said that the weather resistance is sufficient.
In addition, an oxypropylene polymer having a crosslinkable silyl group capable of curing into a rubber-like substance by virtue of moisture or the like has been conventionally utilized, for example, in an elastic sealant for structures or the like. In this case, a composition obtained by blending the polymer with a plasticizer, a filler, and the like has been utilized in terms of physical properties and of cost. The restoring property of the sealant for filling a joint of the structure plays an important role in following the fluctuation of the joint due to a humidity difference.
Various investigations have been conducted on a curable composition excellent in restoring property (see, for example, Patent Documents 5 and 6). However, the physical properties of the composition such as weather resistance and paint anti-staining property have been poor.
Further, a curable resin composition having fire resistance has been currently produced on an industrial scale, and has been finding use in a wide variety of fields including structure-, automobile-, and electric machinery-related fields. In particular, in a sealing material application, a sealing material superior in fire resistance compared to a conventional one has been requested in association with the recent increase of interest in safety.
Sealing materials each containing a polyphosphate compound as a foaming agent have been known as examples of fire resistant sealing materials that have already been on the market. Of the materials, a material containing ammonium polyphosphate is effective; the generation of an ammonia gas caused by the hydrolysis of the material and phosphorus in the material promote the carbonization of any other substance to cause the substance to produce an incombustible carbonized layer, whereby the material has fire resistance (see, for example, Patent Documents 7 and 8).
However, none of the sealing materials each containing a polyphosphate compound can obtain predetermined fire resistance unless the loading of the polyphosphate compound is equal to or higher than a certain level. Moreover, blending each of the sealing materials with the polyphosphate compound involves the following problems: reductions in physical properties of each of the sealing materials and an increase in cost for the production of each of the sealing materials.
In addition, a sealing material obtained by adding a foaming agent to a vinyl based organic polymer has been known as examples of any other sealing material having fire resistance; the material is formed on the basis of the vinyl based organic polymer having good heat resistance, and the foaming agent in the material expands or generates a gas to form a foaming layer having heat insulating property, whereby the material has fire resistance (see, for example, Patent Document 9).
However, the vinyl based organic polymer is inherently poor in elongation property. In addition, blending the vinyl based organic polymer with the foaming agent involves the following problem: additional reductions in the physical properties of the polymer.
In addition, from the viewpoint of fire resistance, a method of making a part other than a sealing material (mainly a back-up material) fire-resistant has been employed for the purpose of imparting fire resistance to a joint portion. To be specific, the following method has been known: a foaming asbestos body cut to be adjusted to be the width of a joint (for example, trade name “Litoflex” manufactured by NICHIAS Corporation) is inserted under pressure into the bottom of the joint, and, furthermore, an ordinary sealing material is loaded into the upper portion of the resultant, whereby compatibility between fire resistance and water resistance is achieved.
However, such method must be executed by an expert in order that fire resistance may not vary from place to place, and requires the following complicated operation: the body must be cut to be adjusted to be a joint shape that varies from place to place. As a result, the method is extremely costly.
A silicone based sealing material different from the present invention in composition has also been attracting attention because of its excellent flame resistance. However, the material involves the following problems: the material is poor in coating property, and causes water-repellent staining.    Patent Document 1: JP 5-287186 A    Patent Document 2: JP61-233043A    Patent Document 3: JP8-48888A    Patent Document 4: JP2001-271057A    Patent Document 5: JP55-9669A    Patent Document 6: JP01-29821B    Patent Document 7: JP2832222B    Patent Document 8: JP8-253761A    Patent Document 9: JP2001-354830A